The present invention relates to fluid flow detectors for detecting the flow of a fluid through an object. The invention is particularly useful for microvascular monitoring, i.e. for monitoring minute variations in the blood flowthrough skin or other tissue and is therefore described below with respect to this application.
Detection of minute variations in blood flow at the capillary level is essential for the diagnosis of tissue viability in certain conditions, such as in burns, flaps, tissue trauma and ischemia, and central and perpheral circulation disorders. An early and accurate diagnosis of tissue viability is necessary for both optimal treatment and optimal prognosis. Because of the extremely small size of the capillary, and the very slow blood current, the presently used methods have mostly been indirect methods, measuring the effects of blood flow rather than directly measuring blood flow, moreover, they are not very precise and usually provide, at best, merely an estimation of the quantity of blood that arrives from the center to the measured site.
One of the recently-proposed methods for microvascular monitoring is based on the Doppler effect, wherein a high-frequency wave, preferably of laser light but also conceivably of ultrasound, is transmitted via a waveguide, or directly to the site and reflected back to a receiver, the frequency shift between the transmitted and reflected waves being an indication of the blood flow at the examined site. Such detectors show promise for the non-invasive and real-time detection of blood flow, but insofar as we are aware, they have not yet been developed to the point of practical use.